I only have Rodinal at hand. And I'm using Kodak Tri-X 400 shot at Box Speed.
What's the recommended dilution for Rodinal? 1:50 or 1:100 or others.
Stand development or following Mass Dev chart?
There's no useful definition of 'best'. For a long time I used 1+25, now I used 1+50, both using pretty much the massive dev chart's times (and I always use it at 400). 1+25 is possibly a little grainier, but both look fine enlarged to 12x16, assuming what you want is something that looks like a print from 35mm Tri-X.